Conventional paperboard boxes and corrugated containers are often rectangular or octagonal in shape and typically have enclosed bottom portions formed by overlapping flaps. The top portions of such containers may be left open or may be enclosed by similar overlapping flaps or by a separate top cover. Panels on corrugated containers are often constructed of multi-wall corrugated paperboard materials laminated together to meet applicable strength requirements. For example, some heavy-duty corrugated containers for transporting bulk materials have side panels constructed of two or more plies, with each ply including two or more corrugations. Containers of this nature are commonly referred to as “bulk bins,” and are often used to store and transport liquids or granular substances. When used to hold a liquid, a flexible and impervious liner is typically installed inside the bulk bin to contain the liquid and protect the paperboard material from liquid-related damage. This liner will often incorporate a drain fitment that extends through an opening in the lower portion of the bulk bin in such a way that a user can access the fitment to dispense the liquid contents from the bulk bin.
Bulk bins offer certain advantages that metallic containers, such as 55-gallon drums, do not offer. For example, in addition to being recyclable, bulk bins can also be “knocked down” into a substantially flat configuration for ease of storage or shipment, and then resurrected later for use. In the case of a rectangular bulk bin, knocking it down will typically involve removing or deconstructing any top or bottom closures and then compressing two opposite corners of the bulk bin together to thereby flatten the structure. Consequently, in the knocked-down configuration, two opposing corners of the bulk bin will form substantially open angles while the other two corners will form substantially closed angles.
One common problem with conventional bulk bins, however, is that they are often difficult to knock down flat, having a tendency to spring back into a partially erect configuration that is undesirable for storage or transport. One attempt to alleviate this spring back problem is disclosed in U.S. Pat. No. 4,441,948 to Gillard, et al. Gillard discloses a bulk bin that is manufactured by winding corrugated sheet material on a large, rotating, rectangular-shaped forming mandrel. As the corrugated material is wound, a shoe-plate compresses the material toward the mandrel as each corner of the mandrel passes. The result is a bulk bin having compressed material in each corner that allegedly offers less knock down resistance than conventional bulk bins. One shortcoming associated with the bulk bin disclosed in Gillard, however, is the complex manufacturing equipment it requires. In contrast to the conventional manufacturing equipment used to make flat blanks of corrugated material for use in conventional bulk bins, Gillard requires a large, rotating forming mandrel capable of winding corrugated materials into large box-like structures.
Another attempt to develop a multi-ply corrugated container that is easily knocked down to a flat configuration is disclosed in U.S. Pat. No. 6,138,903 to Baker. Baker discloses a multi-ply corrugated container having a rectangular cross-sectioned inner tubular shell concentrically disposed within a rectangular cross-sectioned outer tubular shell. Adjacent walls of the inner and outer shells are offset from each other to form spaces in between in which rectangular panels of corrugated material are inserted and bonded to the adjacent walls. Because the rectangular panels do not extend to the corners, this construction results in gaps between the inner and outer shells at each corner of the container. The corrugations of the inner and outer shells are additionally compressed at each corner so that, apparently, the container can be easily knocked down to a flat configuration without a substantial amount of spring-back.
A further problem often associated with bulk bins for holding liquids is the tendency for the drain fitment to move or rotate during movement of the bulk bin or filling of the liner. Such movement can cause the drain fitment to bear against the periphery of the fitment opening in the bulk bin often resulting in damage to the drain fitment or the liner. In addition, the structural integrity of the bulk bin may be compromised by creasing or breakage of the corrugated panel adjacent to the fitment opening.
A number of fitment retainers attempting to overcome this problem are disclosed in U.S. Pat. No. Re. 33,128 to Nordstrom, U.S. Pat. No. 5,749,489 to Benner, et al., and U.S. Pat. No. 5,803,346 to Baker, et al. In general, these fitment retainers are formed in an end cap structure that encloses the bottom of the bulk bin, and they typically include a fitment aperture of some type intended to prevent the fitment from migrating or rotating during use.